An image forming method employing an intermediate transfer member is known as a method for transferring a toner image hold on a surface of an electrophotographic photoreceptor (“photoreceptor”) to a transferee material conventionally. The final image is obtained by a process such that a toner image on a photoreceptor is primarily transferred to an intermediate transfer member, and then secondarily transferred from the intermediate transfer member to the transferee material in this image forming method. This method is a multiple transfer method wherein an image original is reproduced by utilizing subtractive color process employing color toners such as black, cyan, magenta and yellow, and each color toner image is primarily transferred from the photoreceptor to the intermediate transfer member in sequence and finally all color toners are transferred from the intermediate transfer member to the transferee material at once in a so called full color image forming apparatus
However image defect may be liable to occur due to transfer defect because the multiple transfer method includes two transfer process of the first and secondary transfer, and a plurality of toner images are superposed on the intermediate transfer member the superposed toner image is transferred to the transferee material at once.
It is known that transfer performance can be improved by modifying it such that surface of toner particles is treated with an external additive such as silica for transfer defect of toners in general. However there is a problem of not obtaining good transfer performance because silica particles are released from toner particles or embedded into inside toner particles due to stress suffered from toner stirrer or regulation blade for forming toner layer on a developer roller, or stress suffered between photoreceptor and developer roller.
A method is proposed to improve secondary transfer performance by modifying it such that that surface energy of the photoreceptor is allowed to be lower than that of the intermediate transfer member due to reducing surface energy of the intermediate transfer member (See, for example, Patent Document 1).
The other method is proposed to prevent generation of hollow characters by suppressing aggregation of toner on the intermediate transfer member by modifying it such that improving secondary transfer performance by reducing surface energy of the intermediate transfer member and further introducing elastic layer in the intermediate member (See, for example, Patent Document 2).
However, toner particles are liable to aggregate and this cause problem generating hollow characters frequently because the surface energy of the intermediate transfer member is reduced in the intermediate transfer member described in the Patent Document 1. There was a problem that quality of transferred image is degraded because cleaning performance to remove residual toner is degraded and the surface of the intermediate transfer member is stained by toner or so (toner filming), when printing is continued, for example, 100,000 sheets employing the intermediate transfer member described in Patent Document 2.    (Patent Document 1): JP-A H08-211755    (Patent Document 2): JP-A 2006-79016